The invention relates to a fan-and-filter unit to be mounted in the wall of a switch cabinet or housing, comprising a fan unit inserted in a fan housing, a filter mat arrangement mounted upstream of the fan unit and a fan cover immobilizing the filter mat.
A fan-and-filter unit of this type to be mounted in an opening of a wall of a switch cabinet or a housing is described in DE 198 60 433 B4. The fan-and-filter unit comprises a fan housing in which a fan unit with electromotor and fan wheel for suction of air from the exterior into the interior of the cabinet or for expelling air from the interior of the cabinet is arranged and which is covered towards the outer side by a louvre grid having horizontal lamellae and air outlet openings therebetween. A filter mat is inserted between fan cover and fan unit which in turn is retained at the fan cover by means of a supporting grid. The filter mat retains dirt particles present in the flow path and may become clogged more or less quickly, according to the field of use of the switch cabinet or housing, respectively, and depending on its construction, so that fan efficiency and filtering effect of the fan-and-filter unit may be restricted considerably over time. Thus, it is important to replace the filter mat every once in a while. This is easily forgotten by a user.
Another fan-and-filter unit of this type is shown in DE 93 06 032 U1, wherein also a cross-section of a filter housing may be recognized, which possesses an approximately funnel-shaped construction, so that even in a relatively small fan unit a relatively large air inlet or air outlet opening, respectively, results, which is located in the region of the wall of the switch cabinet or housing and is covered by the filter mat.
Another fan-and-filter unit is shown in DE 10 2004 013 318 B4, that fan-and-filter unit, however, being installed within a larger housing having air inlet and air outlet openings, and a specific flow channel is formed to avoid condensation problems. A filter housing and a fan housing are arranged vertically neighboured with respect to the vertical cabinet wall within the larger housing unit to form a vertical air duct.
A switch cabinet air-conditioning device is shown in DE 197 14 838 C2 comprising, inter alia, an air-conditioning unit in form of a fan as well as a filter mat monitoring means which is part of a superordinate switchgear cabinet monitoring and controlling device in which error data and diagnostic data including switched-on periods may be stored and which may be connected to a personal computer serving as an operating means via an interface. A filter mat monitoring unit of this type is relatively complex and mainly suitable for service staff.